The invention relates to an energy guiding chain for guiding hoses, cables and the like between two connection points relatively movable with respect to each other, said chain comprising a substantially straight lower strand followed by a curved section and a self-supporting upper strand, with several chain straps which are connected to one another via upper and lower cross-members in detachable fashion and assembled into parallel strands, and which overlap one another and can be angled around axes of rotation, where chain straps designed as inner straps with inner overlap areas and as outer straps with outer overlap areas alternate with one another in each chain strand, and where the inner and outer straps are respectively opposite to one another in the two chain strands, and where stops each comprising first stop surfaces for restricting the bending of the curved section and second stop surfaces for restricting the bending of the self-supporting section of the upper strand, and where the stop surfaces of the inner straps are positioned asymmetrically with respect to mirroring at the centre plane containing the axes of rotation.
Energy guiding chains of this kind require different radii of curvature of the curved section as well as different curvatures of the upper strand depending on their various applications. In this way the shape of the upper strand depends essentially on the length of the travel path, the load and other conditions. In this context, a distinction is made between chains with a self-supporting upper strand and chains with a sliding upper strand (following a self-supporting section behind the curved section). In the case of a self-supporting upper strand, the energy guiding chain is freely suspended above the lower strand and the floor. The curvature of the self-supporting upper strand can vary. The super-elevation of the upper strand in the self-supporting section is referred to as pretension. The upper strand of a self-supporting chain can also be straight or sagging. In the case of a sliding upper strand, the energy guiding chain is bent through more than 180xc2x0 in the curved section, so that the upper strand rests on the lower strand after a certain distance. In chains with a sliding upper strand, the distance after which the upper strand rests on the lower strand or the floor is determined by the curvature of the upper strand. In order to prevent the sliding upper strand of a chain from flying up due to the tensile and transverse forces occurring during travel in combination with possible unevenness in the slide rail or in the lower strand on which the upper strand slides, the upper strand is not under pretension in the case of long travel paths.
The bending behaviour of the energy guiding chain is essentially determined by the arrangement of the stops, and the weight of the chain and the lines contained inside.
Energy guiding chains of this kind are known from DE 43 25 259 A1. The chains consist of chain straps connected to one another in detachable fashion by cross-members. The chain straps assembled to form a strand can be angled with respect to one another. In this context, the inner straps and outer straps represent the different types of chain straps. The types differ by, among other things, the arrangement of the overlap areas where they are linked to one another in a manner permitting angling. Based on two chain strands arranged parallel to one another which form a guide cavity, the inner straps/outer straps are those chain straps which are mounted on the inside/outside in the overlap area. Stops are provided in the overlap areas of the chain straps to restrict the angling of the chain straps relative to one another. In this context, the stops in the outer straps are positioned symmetrically with respect to mirroring at the centre plane containing the axes of rotation. The stops in the inner straps are positioned asymmetrically with respect to mirroring at this centre plane.
A disadvantage of the known energy guiding chains is that different inner and outer straps must respectively be provided for different curvatures of the curved section and of the self-supporting section of the upper strand, this increasing the manufacturing and stock-keeping costs.
In reference to this prior art, the invention is based on the task of providing energy guiding chains with different radii of curvature and different upper strand paths, which are simple and economical to manufacture.
According to the invention, the task is solved in that the stop surfaces of the outer straps are positioned asymmetrically with respect to mirroring at the centre plane, such that in case of a change of the orientation of 180xc2x0 either of the inner straps or of the outer straps around the centre axis running in the middle between the two axes of rotation and parallel thereto the self-supporting section of the upper strand and/or the curved section of the chain obtains a different curvature.
By the above-mentioned change of orientation by 180xc2x0 it is meant that the respective straps (inner and outer straps, respectively) are arranged in a position which is rotated by 180xc2x0 around said centre axis in the chain, whereas the other straps (outer straps and inner straps, respectively) maintain their position.
By means of the asymmetrical position of the stop surfaces of the inner and outer straps according to the invention it is possible to realize two different radii of curvature for the self-supporting section of the upper strand and/or the curved section of the chain with only two different types of straps, namely the inner and the outer straps. The prior art required at least three different straps to achieve the same effect.
In a preferred configuration of the energy guiding chain according to the invention, the stop surfaces of the inner straps and the outer straps are positioned asymmetrically with respect to the centre plane in such a way that after changing the orientation either of the inner straps or of the outer straps about the centre axis by an angle of 180xc2x0 the curved section receives a slightly different curvature. With this means, for example, an energy guiding chain with a self-supporting, straight upper strand with pretension can be converted into a chain with a self-supporting, sagging upper strand. A change can also be performed between other shapes of the upper strand.
In a preferred configuration of the energy guiding chain according to the invention, the stop surfaces are positioned mirror-symmetrically with respect to the centre axis of the chain straps running perpendicular to the longitudinal direction of the chain. As a result of this design the straps opposite one another in the chain strands can each consist of identically designed inner and outer straps, this reducing the manufacturing and assembly costs. Furthermore this offers the advantage that the identical inner and outer straps positioned opposite one another in the two chain strands ensure optimum straight running of the chain, since manufacturing defects of separately manufactured opposite straps cannot sum up.
In particular, the chain straps provided for a change of their orientation by an angle of 180xc2x0 are the outer straps.
In a preferred configuration, the stop surfaces of the inner straps are positioned with a relatively strong asymmetry with respect to mirroring at the centre plane containing the axes of rotation, whereas the stop surfaces of the outer straps are positioned slightly asymmetrically with respect to this plane. A change of orientation of the outer straps by 180xc2x0 therefore can lead to the desired change of the shape of the upper strand. Thereby also a change of the radius of curvature of the energy guiding chain in the curved section occurs. This change, however, lies within the range of permissible tolerances, if the asymmetry of the stop surfaces is not too high.
In this context the first stop surfaces of the outer straps can be parallel and the second stop surfaces of the outer surfaces can be slightly inclined with respect to the centre plane containing the axes of rotation.
The chain straps on the outer sides of the chain strands can be provided with a marking in order to facilitate manipulation and accurate determination of the orientation of the chain straps. Thus, the orientation of the straps can always be determined from the relative position of the marking of the inner strap and the outer strap.
In an advantageous configuration of the energy guiding chain according to the invention, double-acting stops, generally known in the prior art, are provided, each of which comprising two stop surfaces for restricting the curvature of the curved section and the self-supporting upper strand, respectively.